Rams

ABSTRACT

In a fluid-operated ram a piston member is reciprocable within a casing and divides the casing into two chambers. One of the chambers is arranged to be connected to a source of driving fluid while the other is arranged to be evacuated whereas the piston member is held by a quick-release mechanism, e.g. a mechanical bolt or an electromagnet arranged to co-operate with part of the piston member.

United States Patent Gournelle 1 Sept. 10, 1974 54 RAMS 2,984,529 5 1961 Dailey 92/85 61 O 1 1 Inventor Paul Goumelle, 1 468 1331333 3/1362 85532151113??? 359.11? Bruyeres, Asniefes, Hams de Seine, 3,027,876 4/1962 Strich 92/15 France 3,082,745 3/1963 Brooks 91/376 3,182,561 5/1965 Arnett 91/47 [22] Sept' 1971 3,230,838 l/1966 Westbrook. 91/42 2 1 App] 17 153 3,605,553 9/1971 Panigati 92/85 Primary Examiner-Edgar W. Geoghegan [30] Foreign Application Prlorlty Data Assistant Examiner A' M. Zupcic Sept. 8, 1970 France 70.32546 Attorney Agent, or 1 E Ross; Herbert D b 52 us. 01 91/51, 91/459, 92/12, H

, V 7 92/15, 92 5, 92/151 51 1111.01 F15b 13/044, Fl5b 15/22, ABSTRACT F15b 15/26 In a fluid-operated ram a piston member is reciproca- 1581 F'eld Search 91/47 9 ble within a casing and divides the casing into two 91/459; 188/313 92/8 chambers. One of the chambers is arranged to be con- 15, 85 nected to a source of driving fluid while the other is arranged to be evacuated whereas the piston member [56] Reiel'ences cued is held by a quick-release mechanism, e.g. a mechani- UNITED STATES PAT S cal bolt or an electromagnet arranged to co-operate 513,601 1/1894 T631 91/47 with part of the piston member.

2,790,424 4/1957 Giladett 92/23 2,866,442 12/1958 Panariti 92/12 5 Claims, 4 Drawmg Figures 2,945,677 7/1970 Kammerer 91/47 2 A 2 4 am 32B 35B 266 3/5 48A [is I! I A/ 485 494 1 5 774 -36fl- 56'5- ZZ? 1 2a 75 49 I 7 Z VACUUM 9 PUMP PAIENIEB 8E? I 01914 amazm sum '1 or 3 Maurice Paul GOURN INVENTOR :karl jams Attorney Pmmmsmmm Y 3.834.276

sum 2 or 3 VACUUM PUMP Maurice Paul scum INVENTOR Attorney 5 PATENIEn SEP 1 o 1914 $||EH3BF3 fla4' I 4 film l 1 I Maurice Paul GOURN INVENTOR m jams Attorney RAMS This invention relates to fluid-operated rams.

It has been proposed to use single-or double-acting rams to obtain rectilinear or rotary displacement of mechanical parts. The speeds of displacement that are obtained are in general relatively slow, seldom in excess of one meter per second. This speed depends on the speed with which pressurized fluid is admitted to and removed from the chambers of the ram and is therefore dependent upon the rate of supply of this fluid which is limited by the dimensions of the supply lines.

This speed is also limited, in the case of a singleacting jack, by the inertia of the return device. As a result, some increase of speed can be obtained by augmenting the pressure of the driving fluid; on the other hand, such a pressure increase may impose unacceptable stresses upon the mechanisms controlled by the ram or jack.

According to the present invention a ram comprises a piston member reciprocable within a casing, the piston member dividing the casing into two chambers one of which is connectable to a source of driving fluid whereas the other is arranged to be evacuated while the piston member is held by a quick-release mechanism.

The quick-release mechanism may be a mechanical bolt arranged to co-operate with the piston member, e.g. by engaging a suitable notch on the piston or the piston rod.

The quick-release mechanism may be electromagnetic and may co-operate with the piston member so that cutting off the current to the electromagnet releases the piston member. In such a case the casing may be cylindrical and one end of the cylinder may form a yoke for the electromagnet while the piston member forms the armature. The pressurized fluid acting upon the piston member with rectilinear or rotary displacement may be a liquid or a compressed gas. In this case, a slowdown of the movement of the piston member due to the limitation of the supply lines for the pressure fluid is unavoidable. Preferably, therefore, the driving fluid is air at atmospheric pressure so that no valves have to be provided for the supply of this fluid and the cross-sectional areas of the supply lines may approximate that of the piston member.

In such an embodiment, the atmosphere constitutes an energy accumulator which is practically unlimited and whose energy is available to operate the piston member when it is released.

However, if the admission of air from the atmosphere is effected toward the piston without loss of pressure and if the vacuum is high enough on the opposite side of the piston member, the latter will execute a uniformly accelerated movement and its speed will be at its maximum at the end of the stroke. This drawback may be obviated by limiting the cross-sectional area through which air is admitted. This limitation may be advantageously adjustable, not only at the start of the piston movement but also possibly during its stroke, and may depend upon the piston of the piston at any one moment.

At the end of the stroke the speed of the piston and of the apparatus associated with it is great and the corresponding energy must be dissipated to stop the movement except in the case where, in fact, a shock is desired as, for example, in hammers. When impact is to be minimized, it is preferable to brake the movement of the piston at the end of the stroke so as to avoid a destructive effect by hammering, as by means of a dashpot in which air is compressed. The braking effect may be obtained by allowing air compressed in the dashpot to escape through apertures of small section.

In certain cases, the compressed air in the dashpot may be used for auxiliary functions in the driven device, for example, in the case of a molding machine for plastic sheet material, to perform blowing and ejection functions for the shaped product.

The invention may be carried into practice in various ways and several embodiments will now be described by way of example with reference to the accompanying drawing in which:

FIG. 1 is a longitudinal section of a first form embodiment of a pneumatic ram according to my invention;

FIGS. 2 and 3 are cross-sections of two alternate embodiments; and

FIG. 4 shows the application of a ram to the forming of plastic sheet materials by stamping.

In the embodiment shown in FIG. 1, a cylinder 1 is closed at one end by an annular plate 2 which has an annular recess containing a winding 3 which is connected to an external current source 21 by leads 4 and a switch 22. The central hole in the plate 2 is connected by a duct 5 to an electrically operated valve 6 of twoway type which enables the right-hand chamber of the cylinder 1 (as seen in FIG. 1) to be placed in communication either with the atmosphere, by a duct 7, or with a vacuum pump 9 through a duct 8.

The other end of the cylinder 1 is closed by a base member 10 which has a slide bearing 11 and a sealing gasket 12 engaging a piston rod 13. The bearing 11 has, in addition, a reinforced peripheral portion 23 which supports a resilient ring 24 serving to damp the movement of a piston 19 against the base member 10.

The base member 10 is, like the plate 2, provided with an opening which communicates via a duct 14 with a two-way electrically operated valve 15 which permits the left-hand cylinder chamber to communicate either with atmosphere via a duct 16 or with the vacuum pump 9 via a duct 17.

A piston head 18 of mild steel has sealing gaskets 19 around its periphery and is secured to the piston rod 13 by a screw 20. In the position shown in FIG. 1, the piston head 18 is held at the right-hand end of the cylinder by the attraction of an electromagnet which is constituted by the winding 3 and the plate 2, its yoke being represented by the winding and the plate whereas its armature is formed by the piston.

It will be assumed that valve 6 has opened the duct 7 to the atmosphere and that a vacuum has been created in the chamber 25 by the pump 9.

On opening the switch 22 the piston is released and the atmospheric pressure acting upon its right-hand face moves it to the left. The speed of this movement depends upon whether the valve 6 is completely or par tially open to the atmosphere. Means -not shownmay brake the movement of the rod 13 to the left. At the end of its stroke the piston meets the ring 24 which damps the force of the impact and stops the movement of the piston.

To return the piston to its original position the valve 6 opens the duct 8 while the valve 15 places the chamber 25 in communication with the atmosphere. The piston resumes its original position in which it is thereafter retained by closing the switch 22.

Mechanical means, e.g. a cam, may return the piston to a position adjacent its original position, the attraction of the electromagnet completing the return movement.

For the movement of the piston to the right, a slight lowering of pressure is generally sufficient. For the working stroke to the left the efficiency and speed of movement depend upon the vacuum reached. However, in practice, the vacuum obtained with the usual piston pumps will be adequate and a l5-Torr vacuum is generally sufficient for most purposes. With such a pressure a ram having a cross-sectional area of 150 cm and a -cm stroke can achieve a speed, at the end of the stroke, of 10 meters per second.

The embodiment shown in FIG. 2 is a double-acting ram, i.e., one capable of high speeds in both directions. The ram has two cylinders 26A and 26B and two piston heads 27A and 27B carried by a common rod 28.

Each piston head is integral with a reduced step forming a boss 29A, 298 which is arranged to enter a cylindrical cavity 30A, 30B of the common base member 31 of the two cylinders.

The chambers 31A and 36B of the two cylinders, which are adjacent the base member or partition 31, permanently communicate with the atmosphere through respective ports opening into ducts 32A and 328 provided with adjustable throttles 33A and 338. Similarly, the cavities 30A and 30B are in communication with the atmosphere via respective ports which open into ducts 34A and 34B having adjustable throttles 35A and 35B.

The chambers 36A and 31B of the cylinders 26A and 268 may communicate alternately with the vacuum pump 9 and with the corresponding atmosphere or vice versa, by means of valves A and 40B. The valve members 37A and 37B thereof each have a channel 38A or 388 in the shape of a V and their valve casings are each provided with one inlet 41A or 41B and two outlets 42A, 42B or 43A, 438. As the chambers 36A and 31B are joined to inlets 41A and 41B, the valve members permit the communication of these inlets with either of their outlets 42A, 43A and 42B, 43B, respectively. The outlets 42A and 42B are connected to the vacuum pump 9 and the outlets 43A and 43B are open to the atmosphere.

The outlets are symmetrically arranged in the valve casings of the valves 40A, 40B while the valve members 37A and 37B are similar and are each connected to one end of a link 45A or 45B, respectively. The other end of each link is pivotally connected to a bar 44 which is moved to the right or to the left by two electromagnets 46A and 468. The shifting of the bar moves the valve members so that the inlet of one valve is placed in communication with the atmosphere while the other is under vacuum and vice versa.

Finally, the piston rod 28 has two notches 47A and 47B co-operating alternately with rotatable keys 48A and 488, respectively, controlled by pins 49A and 498.

In the position shown in FIG. 2, a vacuum is applied to the chamber 36A and atmospheric pressure prevails in the other three chambers 36B, 31A, 313. When the pin 49A is brought to the position 49A,, the mobile structure of the device, that is the assembly integral with the piston rod 28, is driven to the left. At the end of the movement, air is compressed in the cavity 308 and expelled through the throttle 358, which brakes this end of the movement.

Pin 48B is then raised to its phantom-line position to secure the rod 28 in place while the electromagnet 46A is excited. In a few seconds, the device is ready to perform its run to the right.

Operation is in this case symmetrical and in both directions the speed of movement'of the pistons may be the same.

In the alternative embodiment shown in FIG. 3, the ram comprises a casing 50 having a sector-shaped cross-section and a blade 51 integral with a shaft 52 which is movable within the casing 50. A flat 52a in the shaft co-operates with a sliding bolt 53, which is reciprocable by two electromagnets 54 and 55. Thus the shaft can be released at the appropriate moment and the shaft 52 can then be aligned with a recess 53 in the slider 53 to enable the blade 51 to move.

As before, an electrically operated valve 56 makes it possible to create a vacuum in the chamber 57 while atmospheric pressure acts upon the other face of the blade through openings 58.

In the embodiment shown in FIG. 4, the rod 13 of a ram comprising the cylinder 1 and the base member 10 of FIG. 1 is integral with an ancillary piston 60 and an extension 61 ending in a resilient bumper 62.

The piston is movable in a dashpot 63 which passes through a floating plate 65 provided with guiding rods 64 and punches 66 intended for stamping containers from thermoplastic sheet material. The dashpot 63 contains a return spring 67 for the piston 60. On the end of the dashpot nearest the cylinder 1 there is a closure plate 68 which allows free passage of air and carries a shock-absorber ring 69, while the opposite end of the cylinder is closed and communicates with the interior of the punches through channels 70 in the plate 65 and an orifice 71 in each of the punches. A pin 72 sliding against a spring 73 forms the end of each punch, air being free to pass around the periphery of the pin.

This device operates as follows:

When e. g. by means of an electromagnet, the rotating key 48 (FIG. 2) which retains the rod 13 is actuated, the rod moves downwardly in FIG. 4 and carries with it the dashpot and the plate 65 with its guides and punches. This joint movement takes place by virtue of the spring 67 and the friction between the gasket of the piston 60 in the dashpot 63.

When the punches stamp the sheet of thermoplastic material and sink into the shaping dies confronting them, the advance of the punches is retarded, and the piston 60 moves relative to the dashpot 63 braking by air compression the movement of the piston 18 head 18 (FIG. 1) in the cylinder 1.

When the punches reach the bottom of the dies, the spring 67 is compressed, the bumper 62 touches the bottom of the dashpot 63 and compressed air is trapped in a well of the dashpot and in the ducts 70, 71.

At the end of the stamping operation each container formed by a punch has been cut from the surrounding sheet so that normally each stamped container tends to .adhere to the punch which formed it and to be carried away with it in its return movement.

However, the compressed air in the dashpot 63, as soon as the movement of withdrawal of the punches has begun, may expand into the space between each container and its punch, thereby separating the punches from the containers and also enabling the punches to be retracted freely even as it cools the containers. The containers then remain in the dies which are provided with ejectors to push them out after complete withdrawal of the punches and lateral freeing of the dies.

The embodiment shown in FIG. 1 may be used to form containers from heated thermoplastic sheets, by means of punches shaping the sheets. It may also be used for pick, riveting or perforating hammers, or for stamping or cutting presses.

The embodiment shown in FIG. 2 is suitable for the transfer of parts to be machined and also for double stampers or punches.

The embodiment of FIG. 3 is suitable for devices intended to lock screwed members or for twist riveting.

What I claim as my invention and desire to secure by Letters Patent is:

1. A pneumatic ram comprising:

a casing provided with a fixed transverse partition;

a piston member reciprocable within said casing, said member being provided with a pair of piston heads on opposite sides of said partition forming two inner chambers close to said partition and two outer chambers remote from said partition, said partition being provided with oppositely facing cavities and with restricted passages connecting said cavities to the atmosphere; a source of vacuum; valve means for alternately connecting said outer chambers to said source of vacuum and to the atmosphere, thereby reciprocating said member between two limiting positions, said piston heads being integral with bosses receivable in said cavities in respective limiting positions of said member to cushion the impact of arresting same; and

retaining means for releasably arresting said member in either of said limiting positions.

2. A ram as defined in claim 1 wherein said valve means is provided with electromagnetic actuating means. I

3. A ram as defined in claim 1 wherein said passages are provided with adjustable throttles.

4. A ram as defined in claim 1 wherein said retaining means comprises an electromagnet.

5. A ram as defined in claim 1 wherein said source generates a vacuum on the order of 15 Torr. 

1. A pneumatic ram comprising: a casing provided with a fixed transverse partition; a piston member reciprocable within said casing, said member being provided with a pair of piston heads on opposite sides of said partition forming two inner chambers close to said partition and two outer chambers remote from said partition, said partition being provided with oppositely facing cavitIes and with restricted passages connecting said cavities to the atmosphere; a source of vacuum; valve means for alternately connecting said outer chambers to said source of vacuum and to the atmosphere, thereby reciprocating said member between two limiting positions, said piston heads being integral with bosses receivable in said cavities in respective limiting positions of said member to cushion the impact of arresting same; and retaining means for releasably arresting said member in either of said limiting positions.
 2. A ram as defined in claim 1 wherein said valve means is provided with electromagnetic actuating means.
 3. A ram as defined in claim 1 wherein said passages are provided with adjustable throttles.
 4. A ram as defined in claim 1 wherein said retaining means comprises an electromagnet.
 5. A ram as defined in claim 1 wherein said source generates a vacuum on the order of 15 Torr. 